Multi levels prop support and fixes for dijit/form/FilteringSelect and dijit/form/Select

Dojo-props
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Before this commit, ```data-dojo-props="constraints:{min:0}"``` doesn't work as
the current implementation support only one depth level of property.

dijit/form/Select and dijit/form/FilteringSelect
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When using those widget, it's better to use the item field instead of value
to fit the angularjs way of doing things.